Add more unit tests

[LinuxSuRen]

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[codecov-commenter]

Codecov Report

Merging #26 (66e543d) into master (33484d0) will increase coverage by 32.96%.
The diff coverage is 81.63%.

@@             Coverage Diff             @@
##           master      #26       +/-   ##
===========================================
+ Coverage   56.82%   89.79%   +32.96%     
===========================================
  Files           2        2               
  Lines         227      245       +18     
===========================================
+ Hits          129      220       +91     
+ Misses         95       17       -78     
- Partials        3        8        +5     

Flag	Coverage Δ
unittests	89.79% <81.63%> (+32.96%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
main.go	86.18% <81.63%> (+46.31%)	⬆️

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